Pulp-screen



No. 6l2,404. H Patented Oct. l8, I898. D. B. DAVIS.

PULP SCREEN.

(Application filed Nov. 1, 1897.) {No Model.)

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No. 612,404. Patented Oct. l8, I898. D. R; DAV|$. PU'LP SCREEN. A ucam nfiled Nov. 1, 1897.)

3 Sheets-Sheet 2.

(No Model.)

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No. 6|2,404. Patented 00f. l8, I898.

n. n. DAVIS.

PULP SCREEN.

. (Application filed NW. 1, 1897.) (No Model.) v- 3 Sheets-Sheet 3.

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DAVID R. DAVIS, OF EAU CLAIRE, WISCONSIN.

PULP-SCREEN.

SPECIFICATION forming part of Letters Patent No. 612,404, dated October18, 1898.

Application filed November l, 1897. Serial No. 657,063. (No model.)

T0 aZZ whom it may concern:

Be it known that I, DAVID R. DAVIS, a citizen of the United States,residing at Eau Claire, in the county of Eau Claire and State ofWisconsin, have invented certain new and useful Improvements in PulpScreens, of which the following'is a specification.

The object of my invention is to separate by improved devices the finefibers of paperpulp from the coarse fibers or slivers thereof.

I provide a rotary cylindrical screen and a flow-box from which the pulpto be screened is delivered and from which it passes to a distributerthat feeds it to a revolving cylinder. The fine fibers or particles ofthe pulp pass through the meshes of the screen, while the coarser fibersand slivers are delivered to a I carrying-off trough, or the fineparticles may be made to pass through the screen into a carrying-offtrough, while the coarser fibers are carried away in other ways. Theflowbox is so arranged as to deliver the wet pulp to the screen in acomparatively thin sheet and the screen is arranged above the waterlevelin the receptacle below it. The flowbox and the carrying-off trough arearranged to extend throughout the entire length of the working surfaceof the cylinder, and the organization is such that the finerparticles ofpulp are made to pass through the cylinder without any longitudinalmovement thereof, and the coarser particles are moved vertically andWithout longitudinal move'ment,separated from the finer particles, anddelivered to devices which carry them away from the screen. In order toseparate the coarser fibers or slivers from the cylinder, I employaspraypipe which causes jets of Water to impinge against the cylinder,pass through the meshes thereof, separate the particles of pulptherefrom, and direct them into a receptacle provided for them and bywhich they are carried away. Ordinarily the fine particles or thegreater portion of them will pass through the meshes of the screen assoon as theyfall onto the surface of the cylinder, the'water with whichthey are mixed being generally sufficient to wash them through themeshes; but in order to promote the screening and to Wash through I thescreen any small particles that might adhere after the water that camefrom the flow-box has passed through the screen I preferably employ oneor more. spray-pipes which cause jets of water to flow over thescreenand wash through it the remaining small particles that may beadhering. Generally speaking, the screen is self-cleaning, and a newclean surface is constantly being presented in front of the spillway ofthe flow-box to receive the wet pulp therefrom. Sometimes, however,especially when working with green wood, there is a gummy deposit uponthe screen after it has been used for some time and it is desirable touse some additional means for cleaning it. I therefore provide aperforated pipe running longitudinally of the cylinder and cause steamto pass through it and into the meshes of the screen,

so as to cause the gummy matter and other clogging material to beseparated. It is only necessary to clean the screen with steamoccasionallythat is to say, after it has become clogged from continueduse.

. The details of construction will be l1erein-' after more fullydescribed; but I wish it understood that my invention is not confined tothe details of construction shown in the drawings and hereinafterspecified, but irrespective of these details consists particularly inproviding an unsubmerged screen to which the wet pulp to be screened isfed from the flow-box, which delivers the wet pulp in a thin sheet fromend to end of the working surface of the cylinder, or practically so,and in providing means practically coextensive with the flow-box forcarrying oif the material that does not pass through the screen. In theaccompanying drawings, Figure l is an end elevation of an apparatusembodying myimprovements. Fig. 2 is a perspective View of the flow-box.Fig. 3 is a plan View of the flow-box. Fig. 4 is alongitudinal sectionthrough the apparatus on the line 4 40f Fig. 1. Fig. 5 is a plan viewwith some of the parts broken away.

The cylinder A is composed mostly of perforated sheet metal incylindrical form, with suitable frames or flanges at the ends to stiffenit. It is, however, without spokes, and it is open at each end. Thecylinder rests on small carrying-wheels 13, mounted in suitable bearingson a supporting frame 0. The shafts b of the rollers may extend from endto end of the cylinder, and one of the shafts carries a pulley D, towhich power may be applied. By suitable gearings both shaftsmay bedriven from this pulley. In this Way the cylinder may be made to revolvein the direction indicated by the arrow in Fig. 1. In order to stiffenor strengthen the cylinder, annular ribs a may be formed on or securedto it at proper intervals, as indicated in- Fig. 4 The cylinder isarranged over a receptacle E, adapted to receive the water which passesthrough the screen and also the fine particles of pulp that are carriedthrough by the water. This receptacle has .end pieces extending up alongthe side of the cylinder and carrying rollers e, which bear against theend flanges a and prevent end-wise movement of the cylinder and alsolateral movement thereof. As will be seen by a close inspection of Figs.1 and 4c, the bottom of the cylinder is arranged above the top of thetrough or receptacle E, and is therefore unsubmerged, being above thewater-level in the receptacle.

The flow-box F extends, preferably, from one end of the cylinder to theother. It is preferably arranged inside the cylinder, and, as shown inthe drawings, it is supported on brackets G, secured to the receptacleor box IE, outside of the edges of the cylinder. A delivery-pipe Hpasses through one end of the flow-box and extends to near the middlethereof, where it is provided with an elbow I, that delivers upwardly. ApartitionJ, arranged below the upper edge of the flow-box and above theelbow I, holds down the pulp as it is delivered, but permits it to flowthrough openings j. (Shown clearly in Fig. 3.) The wet pulp passes overonto the top of the partition J and then out over the edge of theflow-box and falls onto a distributer or spreader L, that delivers tothe cylinder A.

A carrying-off trough M is arranged in the upper part of the cylinderabove the flow-box and is supported on brackets m, as indicated in Fig.l. The trough is inclined, is imperforate, and is provided with adelivery-pipe N at its lower end. The apparatus, as shown in thedrawings, is equipped with three water spray pipes N, O, and P, thepipes N and 0 being arranged inside the cylinder and the pipe Poutsidethereof. WVater is supplied to all of these pipes through theservice-pipe Q, and branch pipes lead from the pipe Q to thespray-pipes, which latter preferably extend from end to end of thecylinder. The pipes may be equipped with suitable valves to regulate thesupply. I preferably also employ a steam-pipe R, extending from end toend of the cylinder, and it is perforated to permit steam to impingeupon the cylinder and to force through it any material that may belodged in the meshes thereof. This pipe is only occasionally used toclean the screen when clogged with gummy matter, &c., after constantuse. I

I do not wish to be confined to the precise manner of mounting thecylinder or of ar-.

ranging the flow-box and carrying-off trough. For convenience, as wellas for obtaining the best results, the flow-box is arranged inside thecylinder and the carrying-off trough is arranged above the flow-boxwithin the cylinder. The water that flows out from the flow-box isusually sulficient to wash the fine material through the screen, andtherefore it is not always necessary to employ spray-pipes for supplyingadditional quantities of water for this purpose. The water supplied bythe spray pipes N and 0 should be in small quantities and should not actto force the material through the meshes of the screen, but merely actto gently wash the fine material adhering between the meshes of thescreen into and through the meshes thereof without tending to force thelarger particles or slivers 'therethrough. It is not essential that asteam-pipe should be used to clean the cylinder, as the cylinder islargely self-cleaning; but it is sometimes desirable to employ such anadditional cleaning device, and I find it advantageous to use itin orderto obtain the best results.

The operation of the apparatus is very simple. Brieflystated, it isasfollows: The pulp is brought in by the pipe II anddelivered by theelbow I to the flow-box. It then rises through openings j and fiows overthe partition J, and then over the edge of the spill way Z and fallsonto the distributer or spreader L, which delivers it into the interiorof the cylinder whileit is revolving in the direction indicated by thearrow. The fine fibers of the pulp pass through the perforations in thecylinder with the water and the slivers and coarse pulp stay in thecylinder, adhere to the inner surface thereof, and are carried by itaround past the pipes N and 0 up to the trough M. As before stated, itis not essential that the pipes N and 0 should be used, inasmuch as thewater that passes out of the flow-box is usually sufficient to carry allthe fine particles through the screen, and this occurs within a smallarea just at the side of or below the flow-box; but the pipes N and 0may be employed, if found necessary, to obtain the best results andinsure perfect work. There is no liquid standing in the cylinder at anytime, the liquidlevel being below the bottom of the cylinder, and thecoarse particles and slivers which adhere to the interior-of thecylinder are comparatively dry or only moist. 'When they reach thetrough M, jets of water from the spray-pipe P impinge against them anddrive them into the trough, a sufficient quantity of water being derivedfrom the jets to flow the material down the trough to its destination.

A machine constructed like that just described has been found toseparate approximately ninety-five per cent. of all the fine particlesof pulp from the wet pulp delivered from the flow-box. This fine pulp,which is received into the receptacle E, is carried off from it by anysuitable passage E and is pref- IIC erably treated in a diaphragmscreen,by

l which small particles of sawdust and the like may be separated. Theother five per cent. of material which passes into the trough M flowstherefrom through the pipe N and may be utilized or treated in anysuitable way.

My machine is so constructed that it may be operated at high speed. Thematerial delivered from the flow-box is immediately screened, the waterand fine particles passing through the meshes of the screen immediately,while the coarser particles are carried only part way around with thecylinder without longitudinal movement. They are separated before thecylinder has completed a revolution. Therefore clean portions of thescreen are constantly being presented to the flow-box, and the operationof screening can be very rapidly performed. If the cylinder werearranged above the level of the liquid which passes through the cylinderand the liquid pulp were fed in at the end of the cylinder, the waterwould immediately pass through the meshes of the screen and leave thepulp in a thick mass on the surface thereof. 011 the other hand, if thecylinder were arranged below the liquid-level in the receptacle below ita large surface of the cylinder would-be'kept constantly clogged, thecylinder would have to work through the liquid, and a constant agitationwould be necessary in order to keep the meshes of the screen open; butby having the cylinder arranged above the liquid-level, supplying theliquid thereto in thin sheets along its entire length, these objectionsare obviated, the cylinder is constantly kept clean, and the operationof screening is both rapid and efficient.

I claim as my invention- 1. The combination of an unsubmerged screen, aflow-box arranged Within the screen and delivering liquid pulp from endto end of the working surface thereof, a carrying-0E trough arrangedabove the flow-box, and a spray-pipe outside the screen for forcingparticles of pulp from. the screen into the carrying-off trough.

2. An apparatus for screening pulp, comprising a rotatable screen, aflow-box extending approximately along the entire working surface of thescreen and delivering liquid .pulp thereto, a receptacle below thescreen provided with means for keeping the liquidlevel thereof below thescreen, and a trough extending approximately along the entire workingsurface of the screen for collecting the unscreened material anddelivering it.

3. The combination of an unsubmerged screen, a fiow-box extendingapproximately along the entire working surface of the screen anddelivering liquid pulp thereto, a carrying-off trough extendingapproximately along the entire working surface of the screen forcollecting the unscreened material'and delivering it, and means forseparating pulp fibers from the screen and driving them into the trough.

4. The combination of an unsubmerged screen, a flow-box extendingapproximately from end to end of the working surface of the screen fordelivering liquid pulp thereto, a carrying oif trough extendingapproximately along the entire working surface of the screen, areceptacle below the screen provided with means for keeping theliquid-level thereof below the screen, and a water-spray pipe forseparating particles of pulp from the screen and driving them into thecarrying-0E trough.

5. The combination of an unsubmerged screen, a flow-box arranged withinthe screen and extending approximately from end to end of the workingsurface thereof and delivering liquid pulp to the screen, a carrying-ontrough arranged above the flow-box within the screen and extendingapproximately from end to end of the working surface of the screen, anda spray-pipe outside the screen for forcing particles of pulp therefrominto the carrying-off trough.

6. The combination of the unsubmerged screen, a flow-box arranged withinthe screen and delivering liquid pulp from end to end of the workingsurface of the screen, a carryingofi trough arranged above the flow-box,a water-supply pipe within the screen below the flow-box, and awater-supply pipe outside the screen for forcing particles of pulp fromthe inner surface of the screen into the carryingoff trough.

7. The combination of a rotatable screen, a flow-box extendingapproximately along the entire working surface of the screen anddelivering liquid pulp thereto, a trough extending approximately alongthe entire working surface of the screen for collecting the unscreenedmaterial and delivering it, and a water-spray pipe arranged at one sideof the trough and above it for driving the unscreened material into thetrough.

In testimony whereof I have hereunto subscribed my name.

DAVID R. DAVIS. Witnesses:

WM. A. TEALL, WM. RICHARDS.

